Automatic train-control system



Oct. 30, 1928. C. '5. BUSHNELL AUTOMATIC, TRAIN CONTROL SYSTEM Original Filed oc'c. 25, 1923 FIG- 2..

w'ATTORNEY fill Patented 0st. 39, 1928.

UHTED STATES 1,689,228 ATENT OFFICE.

CHARLES S. BUSHNELL, OF ROCHESTER, NEW YORK,'ASSIGNOR TO GENERAL RAIL WAY SIGNAL COMPANY, OF ROCHESTER, NEW YORK. I

AUTOMATIC TRAIN-CONTROL SYSTEM.

Original application filed October 25, 1923, Serial No. 670,701, now Patent No. 1,620,188, dated March 8, 1927. Divided and this application filed November 26, 1926. Serial No. 150,901.

This invention relates to automatic train control systems, and more particularly to systerns of the intermittent inductive type.

The present application is a division of my application, Serial No. 670,701, filed ()ctobcr 1923, now Patent 1,620,188, March 8, 1927, for train control.

In providing apparatus for automatically controlling a train in accordance with traffic conditions aheac, it is desirable to be able to automatically restrict the speed of a train in a caution block if the train is to be brought to a predetermined low speed or to a stop before reaching the end of such a block, and to enforce a low limiting speed throughout the following or danger block providing traffic conditions have not cleared up in the meantime. On account of the speed at which the train may be running, weather conditions, the collection of ice and snow, and for various other reasons, it is found difficult to transmit control influences by physical contact between vehicle carried devices and cooperating devices located along the trackway. In providing means for transmitting control influences which are intended to restrict the movement of the train it is highly important that such influences be invariably transmitted under danger traffic conditions ahead, regardless of the speed of the train; whereas the transmission of restoring control influences need not necessarily be effective at all speeds, because the failure to receive a restoring or resetting influence merely causes the movement of the train to be unnecessarily restricted and therefore is on the side of safety.

With the above and other considerations in mind the principal object and purpose of the present invention contemplates the provision of means to transmit restrictive control influences from the trackway to a moving vehicle inductively by the employment of alternating current and effective at all speeds and which means is constructed on the normally closed circuit principle so that the failure of a circuit will cause the transmission of a control influence and restrict the movement of the train regardless of traffic conditions ahead, and to provide means for transmitting a restoring influence which is dependent on a source of direct current energy and possibly is effective only for speeds above a predetermined low speed and which is constructed entirely .on the open circuit principle so that the failure of a circult prevents the transmission of a restoring control influence, thereby also functioning on the side of safety 0 More specifically it is proposed to provide an inert trackway device which is adapted to reduce the reluctance of a magnetic circuit including a car-carried core upon passage of the car-carried core by said trackway device under predetermined traffic conditions ahead, whereby flux is diverted from leakage paths and caused to pass instead through a secondary coil thus causing a higher opposing voltage in the'circuit and causing de-energization of a relay.

Other objects, purposes, and character istic features of the invention will appear as the description thereof progresses.

In describing the invention in detail reference will be made to the accompanying drawings in which Fig. 1, illustrates conventionally one an rangement of trackway circuits and devices embodying the present invention; and

} Fig. 2 shows, diagrammatically, cooperating car-carried apparatus in which the various devices have been shown conventionally. 7

Track equipment.

Referring to Fig. 1 of the drawings, there has been shown a trackway of the usual construction including the rails 1 which are divided by insulating joints 2 into blocks in the usual manner, the block I and the adjacent ends of two other blocks H and J having been shown; since the various blocks are the same like parts thereof have beengiven the same reference characters with distinctive exponents. Each of the blocks is provided with the usual trackway battery 8 at the exit end thereof and a track relay 4 at the entrance end, the direction of traffic being from left to right as indicated by the arrow. At the entrance end of each block is preferably provided a way-side signal of the usual type; although these signals may be of the color light, position light or semaphore type, for convenience semphore signals Z have been shown conventionally without illustrating their well-known control devices and circuits, these devices and circuits being well-known by those skilled in this particular art. In addition to the track relay 4 at the entrance to each block there is provided a line relay 5, which is under normally clear traffic conditions energized by a circuit ineluding the front contact 6 of its associated track relay and the front contact 7 of the track rela of the block next in advance, so that the line relay is energized, providing .both the corresponding block and the block next in advance are unoccupied. This cir-' cuit receives its energy from a suitable source, such as a battery having terminals one of which has been designated 13, the other terminal being connected to a common return Wire C. This source of energy may comprise any number of batteries as for instance one for each block or may consist of a transmission line for supplying a series of blocks.

' 0n the right hand side of the traekway and just before the entrance to each block is provided a knock-down element 'KD, comprising a magnetizable core 8 of general U- shape terminating in enlarged pole pieces 9 having. a coil 1O on the back yoke thereof, which is normally maintained in a closed circuit of low resistance by the front contact 11. of the line relay'5.

In series with the track circuit of the block in the rear, that is, in series with the track battery 3 is connected a relay DL which for convenience may be called a series relay. This relay DL is designed so that its front contact 12 is, under clear trailic conditions, in the lower or de-energized position. If, however, a train occupies the track circuit including this'relay DL sufficient current is caused to flow in the track circuit in question to effectively energize this relay DL and close its front contact 12. If desired this relay may be designed so that it will not assume its energized condition until a train very closely approaches the exit end of. the block. it being understood that the track circuit current gradually increases as the train approaches the track battery 3.

()n the left side of the trackway is provided a similar track element RS conveniently called the restoring or resetting track element, which comprises a core 15 of genoral U-shape terminating in enlarged pole pieces 16 and having a coil 1'7 on the back yoke thereof. As is obvious from the circuit shown in Fig. 1 of the drawing this coil 17 is energized by current derived from the battery 18, or other suitable source ofenergy,

providing the block at the entrance to which the element BS is located is unoccupied and the series relay L is in the energized condition, but is closed in a circuit of low resistance when said block is occupied and the series relay DL is in its energized condition, for reasons more clearly pointed out in con nectionwith the operation of the system. In other words, the knock-down element KD has its coil closed in a circuit of low resistance under clear trafiie conditions in the block at the entrance to which it is placed, but has its coil open under caution and danger conditions of such block, whereas the restoring or resetting element RS has its coil closed in a circuit of low resistance under danger traflie conditions in the block at the entrance 'to which it is placed but has its coil energized by a source of electrical energy under clear and caution conditions of said block providing the series relay BL is in its energized condition.

Carr-carried, devices.

Referring to Fig. 2 of the drawing there has been conwaitionally illustrated a 1 way vehicle by the axles and 26 and asso iated car wheels 27 and 28.

On the right side of the vehicle illustrated, a suming it to be me ing in the direction as indicated by the arrow in Fig. 1, is provided a car element L comprising a core of general inverted U-shape having depending legs terminating in enlarged pole pieces 51. On the rearwardly disposed leg of the core 50 is a primary coil P, which is normally energized by alternating current, from a source not shown) and a secondary coil S in which voltage is induced by wellknown transformer action. On the other leg of the core 50 is provided a secondary bucking coil SB, which is connected in series with the secondary coil S so that the voltage induced therein is opposite to the voltage induced in the secondary coil S. This car element L is suitably mounted on the truck of a railway vehicle, such as a tender truck, and is preferably supported by initially tensionec springs so that it is under ordinary conditions rigid with respect to the truck, but is adapted to move with respect thereto in of severe jars, and the like. This element is so supported that it magnetically cooperates with one or the other of the track elements KI) or RS through an intervening air gap depending on whether the vchicie is moving pilot or tender first. On the left hand side of the vehicle is provided a similar ear element L, which element L identical in construction with the car element L and for convenience like parts have been given like reference characters with the distinctive exponent a.

0 79cm tion.

CZear t0 caution-.9111 order to illustrate the operation of the system under various traffic conditions ahead, let us assume that the block J is occupied, or presents dangerous traiiic conditions for some other reason, so that its track relay i is ale-energized, Let us further assume that a train equipped with suitable car-carried apparatus in its normal clear condition and is moving in the block H in the normal direction of traffic. With the track relay 4 de-energized the circuit for the line relay 5 is broken thus tie-energizing this line relay, thereby putting the coil 10 of the trackelementKD in an open circuit. As the train approaches the signal Z, which is now indicating caution, the left hand car element first comes into communication with the resetting track element RS. Since, however, the car-carried apparatus is in its normal condition the operation that takes place at this time need not be considered. After a further short distance of movement of the train the right hand car element L comes into cooperating relation with the track element KD. While the car element L is disposed over the track element KD during its movement along the track the pole pieces 51 of the car element L are momentarily bridged by the core of the track element Kl), thereby reducing the reluctance of the magnetic circuit including the car-carried core 50. This decrease of the reluctance through the core 50 causes a considerable increase in the alternating current magnetic flux passing through the coil SB. This increase of magnetic flux is due, to a large extent, it is believed, to diversion of flux from leakage paths. The total flux through the primary coil is maintained substantially constant by reason of the law governing the flow of exciting current to transformers, and the like. Since the amount of flux passing through the coil SB has been considerably increased by reason of the presence of the track element KD, and

since. as just explained, the total flux pas ing the primary coil has not been materially changed, it becomes apparent that the voltage induced in the coil S13 is considerably larger whereas the voltage induced in the secondary coil S has been practically unchanged. Further, since the voltage induced in the coil S is no longer capable of predominating over the voltage induced in the coil SE. at least not to an extent to maintain a suitable control stick relay (not shown) energized. such control relay momentariiy assumes its de-energized position at the time the car element L is in cooperating relation with the track element Kl). This momentary de-energization of the control relay causes a front contact thereof to be opened. T he opening of this front contact interrupts the energizing circuit for the control relay permanently, so that the return of the conditions of the car element to normality will not again energize this control relay. With the control relay in its tie-energized position a contact (not shown) assumes its lower position and thereby ole-energizes a train control device (not shown) and effects a re striction in the speed depending on the construction of this train control device. The train may now proceed in block I in accordance with the restriction enforced by the train control device thereby bringing the tram to a lowor minnnum speed, or to a stop, by the time it reaches the end of the block I. For illustration of the various parts, above and below referred to but described as not shown, reference should be had to Patent 1,620,188 referred to above.

Caution 250 caution.Let us assume that the train which formerly occupied the block 5 has advanced out of block J into the next block in advance so that the track relay 4? again assumes the energized position. As the train in question reaches a position in the block I at which the car element L comes into communicating relationship with the resetting track element RS a restoring control influence is transmitted. This restoring control influence is transmitted by reason of the car element L moving over the track element RS While this track element is energized by direct current. The passage of the car element L over the energized resetting track element RS causes a rapid building up and breaking down of Since the train ahead is still in the block neXt in advance of the blocliJ, as heretofore assumed, the line relay 5 is in its deenergized position thereby putting the track element KD in its abnormal active condition. As the train proceeds a little further, its passage by the element KD causes the train carried control relay to respondthe same as it did when the train entered the block 1, thereby again putting the speed restricting device in its active condition the same as when the train in question moved from a clear into a caution block.

Caution t0 dcmger.Had the train which formerly occupied the block J still been in this block J the front cont ct 13 of the track relay 4? would have assumed its lower position thereby completing a circuit of low resistance for the coil 17 of the restoring track element RS as soon as the series relay DIR- became energized, it being assumed that this relay DL assumes its energized position when a train enters a block, such as the block I. lVith the coil of the restoring track element RS closed in a de-energiZed circuit no voltage would have been induced in the coils SB and 1? of the carthe block J; and if no restoring influence should be communicated at the end of the block J the restriction in the speed of the train would persist.

Clear to Zea.Let us now assume that the train is moving in the normal'direction of traflic in the block H under clear trafiic conditions of the blocks I and J, and with the car-carried apparatus in its normal clear condition. As the train occupies the block H the series relay DL assumes its energized position by reason of the. increased current flowing in the track circuit of the block H. The energization of this series relay DL, bearing in mind that the track relay 4 is energized, causes the restoring track element IRS to be energized. As the car element L passes over this track element RS there is no changing'ot the condition of the car-carried apparatus. After a further short distance of movement the right hand car element L comes into communicating relation with the track element KD. Very little current changes, if any, take place in the upper winding of the control relay during the passage of the car element L over the track element KD under this condition, that is, with the coil of the track element KD closed in a circuit of low resistance. One reason whereby this diilerence in the action of the car-carried apparatus may be accounted for when the car element L passes over a track element having its coil closed in a circuit 01 low resistance, is, that the coil 10 of the track element acts as a bucking coil thereby preventing to a large extent the passage of flux through the yoke 8 of the track element KD, so that the reluctance of the car-carried core is not materially reduced although it is disposed directly over the core8 of the track element KD. In other words, the presence of a coil closed in a circuit of low resistance surrounding the core 8 greatly resists and'opposes the passage of flux through this core, so that the flux passing through the bucking coil SB of the carelement L is not materially different even though the car-carried element L is disposed directly over the track element KD in its clear traffic condition. I

Disposition of track elewwats.-The restoring track element BS is located along the track so that it will be encountered before the knock-down element K1) is encountered so that when a. train moves from one caution block int-o a following caution block the speed restricting device may be restored to its energized condition and may then again be initiated when passing over the element KD located just beyond the element RS. This feature is specially desirable in systems in which the train control device is of a cyclic type. For instance, let us assume that a speed restricting device of the type shown in the Simmon Patent 1,150,809 is employed.

While the train is passing through one block its speed will be gradually restricted so as to reach a predetermined low speed upon reaching the end of a caution block, and it the following block has assumed the caution condition in the meantime the speed restrict ing apparatus is restored at the restoring track element RS and is again initiated at the knock-down track element KD, so that 'the speed restriction is removed upon enter- 1 ing the second caution block but the permissive speed is again gradually decreased while the train moves through this second caution block.

In. the particular circuit arrangement shown the track element Kl) must be set back into the preceding block far enough so that the first axle of the train does not enter the block before the car element L has passed'by the track element KD, because if this were possible the train would restrict itself by dropping the track relay and in turn the train control relay. If, however, it is desired to restrict the train only after it has passed a certain distance into caution block, this may be done by controlling the circuit for coil 10 on the track elen'ientl fl) by the track relay oil? the next block ahead, in the same manner as the line relay controls this coil in the circuit arrangement shown.

Having thus shown and described one specific embodiment of the invention, it is desired to be understood that this has been done for illustrative purposes only, rather than for the'purpose of showing the scope of the invention. It is also desired to be understood that various changes and modifications maybe made to adapt the invention train control systems comprising, a track electro-magnet for producing a magnetic held, a source of energ a track circuit, a

relay connected in series with said track cir on it near the energy end of the track circuit, a circuit for energizing said electro-magnet including a front contact of said relay, the winding of said magnet, said source and suitable circuit controlling means governed in accordance with traflic. conditions ahead, whereby said electro-inagnet is only energized under aredetern'nned traiiic conditions ahead provided there is a trainon said track circuit to increase the current in said relay.

2. Trackwa'y apparatus for automatie train control systems comprising, tracks divided by insulated joints into blocks. a closed track circuit for each block including a track relay at the entrance end of the block llU and a source of energy at the exit end, an

fluences to a moving vehicle on said track, a series relay at the exit end of each block connected in series with said track circuit and designed so that it assumes its tie-energized position under normal conditions of the track circuit but assumes its energized position when the track circuit is occupied by a train, and a circuit for energizing said electromagnet including a contact of said series relay closed when the'series relay is energized and circuit controlling means governed in accordance with traffic conditions ahead.

3. Trackway apparatus for automatic train control systems comprising, a track element including a core of magnetizable material disposed along the trackway so as to be in communicating relationship with suitablev car-carried apparatus, a coil on said core, and means for energizing said coil under clear caution traiiic conditions ahead and for connecting said coil in a closed circuit of low resistance under dangerous tra'fiic conditions ahead.

l. Trackway apparatus for automatic train control systems comprising, a track element including a core of magnetizable material disposed along the trackway so as to be in communicating relationship with suitable car-carriedapparatus, a coil on said core, and means for energizing said coil when the track directly ahead is unoccupied and the track directly in the rear of said element is occupied, and for closing said coil in a circuit of low resistance when the track di-' rectly ahead and the track directly in the rear of said elementis occupied. v

5. Trackway apparatus for automatic train control systems comprising, a track element including a core of magnetizable material disposed along the trackway so as to be in communicating relationship with suitable car-carried apparatus, a coil on said core, and means for energizing said coil under clear trafiic conditions ahead and for connecting said coil in a closed(lo-energized circuit under dangerous traffic conditions ahead, 1 roviding there is a train approaching said element from the rear.

6. Trackway apparatus for transmitting control influences from the traclrway to suitable car-carried influence receiving apparatus of train control systems comprising, a track divided into blocks by insulating joints, :1 track relay connected across the rails at the entrance of each block, a series relay and a source of energy connected in series and bridged across the rails at the exit end of each block, said series relay only assuming its energized condition if there is a train in said block, an influence communicating device including a core having a coil tiereon located near the entrance to a block, a control circuit for energizing said coil ineluding a source of energy and a contact controlled automatically. in accordance with trafiic conditions in said block only, said control circuit also including a front contact of the series relay of the track circuit of the next block in the rear, whereby said control circuit is closed only under predetermined tauiic conditions of the first mentioned block provided there is a train in said next block in the rear.

7. Trackway apparatus for inductively transmitting control influences to suitable car-carried apparatus upon passage of trains thereby comprising, a core having projecting poles located so as to be traversable by a suitable car-carried influence receiving means, a coil on said core, means for closing an energizing circuit for said coil, at one point, only under unoccupied conditions of the block ahead of the control point at which said core is located, and a relay connected in series with the track battery of the block in the rear of said first mentioned block having a contact, which is closed when the relay is energized, at another point in said circuit, said relay assuming its energized condition only if there is a train on the track circuit of said block in the rear, whereby said coil is only energized if there is a train approaching said control'point and unoccupied conditions are existing in the first mentioned block. s

8. Trackway apparatus for automatic train control systems comprising, a track element including a core of magnetizable material disposed along the trackway so as to be in communicating relationship with suitable car-carried apparatus,a (oil on said core, means for energizing said coil under clear traffic conditions ahead and for connecting said coil in an inert closed circuit of low resistance under dangerous traflic conditions ahead, an inductor of magnetic material disposed along the trackway to be in communieating relationship with other car-carried apparatus, a coil onthe inductor, and means to open a circuit including the coil, under dangerous traflic conditions ahead.

9. Trackway apparatus for automatic train control systems comprising, a track element including a core of magnetizable material disposed along the trackway so as to be in communicating relationship with suitable car-carried apparatus, a coil on said core, means for energizing said coil when the track directly ahead is unoccupied and the tracli directly in the rear of said element is occupied and for closing said coil in a circuitof low resistance when the track directly ahead and the track directly in the rear of said element is occupied, an inductor of magnetic material disposed along the traclc;

way to be in communicating relationship with other car-carried apparatus, a coil on the inductor, and means to open a circuit lln Ila

ahead, providing there is a train approaching said element from the rear, an inductor of 'magnetic material disposed along the trackway to be in communicating relationship with other car-carried apparatus, a coil on the inductor, and means to open a circuit imluding the coil, under dangerous traflic conditions ahead;

11. Trackway apparatus for inductively transmitting control influences to suitablecarried apparatus upon a passage of trains thereby comprising, a core having projecting poles located so as to be traversible by a suitable car-carried influence receiving means, a coil on said core, means for closing an energizing circuit for said coil at one point only under clear traflic conditions of the block ahead of the control point at which said core is located, a relay connected in series with the track battery of the block in the rear of said first mentioned block having a front contact at another point in said circuit, said relay assuming itsenergized condition only if there is a train on the track circuit of said block in the rear whereby said coil is only energized if there is a train approaching said control point and clear trafiic conditions are existing in the first mentioned block, a magneti'zable inductor on the trackway positioned to be traversed by car-carried apparatus, a coil on the inductor, and means to open a circuit including thecoil, under dangerous traflic condition ahead.

12. Trackway apparatus for automatic train control systems, coinprising,'a track element including a corevof magnetizable material disposed along the trackway in communicating relationship with suitable car-carried apparatus, a coil on said core, and means for energizing said coil under both clear and caution trailic conditions ahead and for connecting said coil in a closed de-energized circuit under dangerous traific conditions ahead, provided there is a train approaching said element from the I rear.

13. Traikway apparatus for automatic train control systems, comprising, a track element including a core of magnetizable material positioned along the trackway for communicative relation with suitable carcarried apparatus, a coil on said core, means for energizing said coil under both clear and caution traffic conditions ahead and for connecting said coil" in an inert ciosed circuit of low resistance under dangerous trai'licconditions ahead, an inductor, of magnetic carried apparatus, a coil on the core, andmeans for energizing said coil when said one block is unoccupied, and the block immediately to the rear thereof is occupied, and for closing said coil in a circuit of low resistance when said one block, and the block immediately to the rear thereof, are both occupied.

In testimony whereof I atlix my signature,

CHARLES S; BUSHNELL. 

